1. Field of the Invention
The present invention relates to a motor control device for vehicle, and more particularly, to a motor control device for vehicle for controlling a motor (electric motor and rotating electric machine) serving as a drive source of a vehicle such as an automobile.
2. Description of the Related Art
It is known that oscillation sources such as a torque ripple generated while a motor is driven generate a resonance of an elastic system such as a suspension of a vehicle in an electric vehicle provided with a motor as a drive source of the vehicle, and a hybrid vehicle provided with both an internal combustion engine and a motor as the drive source of the vehicle. This resonance generates oscillations and noises on the vehicle, resulting in degradation of feel of comfort of passengers.
For example, Japanese Patent Application Laid-open No. Hei 10-23614 proposes a configuration, as a countermeasure for a resonance of a vehicle caused by oscillation sources such as a torque ripple of a motor, for providing torque compensation toward a direction restraining the torque ripple using information on a rotation of the motor.
Moreover, Japanese Patent Application Laid-open No. 2007-221896 proposes a configuration for restraining torque ripple components of a motor torque command value by means of a first-order lag filter using a time constant determined according to a motor rotation speed in order to restrain a torque ripple because the torque ripple according to a variation in the rotation of a motor is generated if the motor torque command value is calculated from an output command value directed to the motor and the rotation speed of the motor.
The resonance of the vehicle refers to a state in which the entire vehicle presents a natural oscillation due to oscillation sources such as a torque ripple on this occasion. The resonance frequency of the vehicle is a natural frequency determined by the weight of the vehicle and spring constants and viscosity coefficients of elastic systems such as suspensions. such as a torque ripple are superposed on the natural resonance In other words, if frequency components of oscillation sources frequency uniquely determined by the vehicle, the superposed frequencies appear as the resonance of the vehicle (see FIG. 4).
The configuration according to Japanese Patent Application Laid-open No. Hei 10-23614 makes a correction of a torque ripple to frequency components other than frequency components of the resonance frequency of the vehicle, and the correction is thus made to the torque ripple components which do not cause oscillations and noises as a result. There is thus a problem that this correction control generates unnecessary higher harmonics, and new oscillations and noises may occur.
The configuration according to Japanese Patent Application Laid-open No. 2007-221896 calculates the torque command value from the output command value directed to the motor and the rotation speed of the motor, and there are thus a problem that the configuration is not suitable for a system driving a motor according to a torque command directed to the motor, and a problem that the first-order lag filter is used, resulting in a correction made to torque ripple components which do not cause oscillations and noises as the vehicle.